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Engine's out, in bits, now what needs replacing? - Esprit 'Project & Restoration' Room - The Lotus Forums Jump to content
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chopwood

Engine's out, in bits, now what needs replacing?

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Guys,

Well my SE's donk is in bits, the head has been re-coed and I'm about to put in a order for all the usual consumables (Bearing shells, gaskets etc). But I'm in a bit of a quandry as to the pistons and liners.

How do I tell if I *really* need to replace the Liners and pistons. I've put the pistons in the calipers and they're all around 95.15mm which is 0.05mm *less* than the technical specs (but not by much 1.9thou").

The question is, how significant is it? Has anyone else here got any experience as to how much wear is acceptable.

I guess what I really need to do is check the liners as it's them that will probably have the brunt of the wear and make the decision. Liners and pistons add fairly significantly to the rebuild cost so I don't really want to replace them unless I have to.

L&K Cain

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Guys,

Well my SE's donk is in bits, the head has been re-coed and I'm about to put in a order for all the usual consumables (Bearing shells, gaskets etc). But I'm in a bit of a quandry as to the pistons and liners.

How do I tell if I *really* need to replace the Liners and pistons. I've put the pistons in the calipers and they're all around 95.15mm which is 0.05mm *less* than the technical specs (but not by much 1.9thou").

The question is, how significant is it? Has anyone else here got any experience as to how much wear is acceptable.

I guess what I really need to do is check the liners as it's them that will probably have the brunt of the wear and make the decision. Liners and pistons add fairly significantly to the rebuild cost so I don't really want to replace them unless I have to.

L&K Cain

I dont think you should need to replace the pistons if they look reasonable, piston rings and bores I think are more important. As to the size of the bores depends how you are measuring them, you say calipers? with a micrometer shoulnt be too bad but you can loose a thou or so if you are using a vernier or digital caliper. I would always measure with a bore gauge if you can get hold of one.


 

"Belief is the enemy of knowing" - Crrow777

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remember before you fit the new pistons and rings, you need to de-glaze the bores, make sure you do this, if youcan get them honed with a cross hatch, its standard procedure to at least de-glaze them before fitting new pistons and rings, failure to do this can cause a few issues, if your told you dont need to de-glaze than tell em to bugger off as it should always be done when you change pistons, it helps them to bed in in very little time and creats the seal better, honing is much better though.

also if you have the crankshaft out have it checked for balance and straightness, it doesnt take long and is worth it, not many people do this, but after speaking with the guys at lotus and doing a ton of research i have found out that its common practice at lotus for them to de-glaze and hone the bores and the get the crank checked.

also while stripped, have the block and parts cleaned in a high temp engine pressure cleaner, its well worth it the people who do the honing etc can do that for you as it will need to be cleaned after the work has been done.

once all is clean get them to check the contact points for all the seals and make sure they are clean and free of debris etc.

if your having your head worked on then have the valve guides replaced with bronze pitted ones, inside the valve guide are tiny little recesses that hold oil in them and lubricate the valve stem, i had mine upgraded as did a few other people on here with these, im pretty sure mike sekinger had them on his race esprit also.

ps: just checked its in the manuals if you look under rebuilding the engine it states in there de-glazing and de-carbonising

Edited by bigsi

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Does that hold true for the nikasil coated liners as well? I know that's standard practice for any cast liners/bores but these nikasil puppies are a bit new to me.

The thing is I can see the crosshatch honing on them still so I figure they can be all that worn (I'm hoping).

I'm definetly going to get the crank done as you suggest, that's just common sense. It's still at the factory dimensions so I've got 20 thou to play with if necessary.

L&K Cain

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get them re-done (re-coated with nikosil). Play it safe in my opinion. I'm having mine done for $160/hole right now. As long as your pistons arent scored... you should be okay. However, be sure to clean the ring-lands before installing new rings.


Modifying esprit's.. now that's fun..

PS... I AM NOT A CERTIFIED MECHANIC.. I Have chosen to help those in need, in the past and must not be construed as being a certified technician.

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heres the info i had from those who know.

when the engine is stripped you should follow the manual for the correct procedure for rebuilding. with older liners prior to refitting new pistons make sure the liners are de-glazed or honed and de-carbonised. with reguards to the nikasil liners de-carbonise them, de-glaze them and if need be get them re-coated as mark suggested.

the crankshaft should be checked for balance and trueness, also check the dimensions are still within spec, if need be get machining done as per the manual.

after work has been done to the engine get it pressure hot washed , the machine shop who do the work should have the washcabinet to do this, as this will remove all the debris from the machine work.

i have just spent two and a half weeks learning everything about rebuilding these engines i can, i have spoken with lotus and with paul matty and several other people and they all say the same thing follow that procedure always.

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